Brake control system



Dec. 2, 1941. H. T. LAMBERT ET AL BRAKE CONTROL SYSTEM 4 Sheets-Sheet 1 Filed m. 4, 1940 67' zzz croz m INV er %Zliam Illll s am I TORNE.

1386- H. T. LAMBERT ET AL 2 5 BRAKE CONTROL SYSTEM Filed Oct. 4, 1940 4 Sheets-Shet 2 (I A I .;'A gm.

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ATTOR Dec. 2, 1941. H. T. LAMBERT ET AL BRAKE CONTROL SYSTEM Filed Oct. 4, 1940 4 Sheets-Sheet 3 H "i if ,1 z

777 zzzzam 22131-3. BY f MM, ATToRwe s- Dec. 2, 1941. i H. T.'LAMBERT ET AL 2,264,537

BRAKE CONTROL SYS TEM Filed Oct. 4, 1940 4 Sheets-Sheet 4 lNV ENTORS. H0776)" 77 Jamie,-

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AT RNEY Patented Dec. 2, 1941 BRAKE oo TRoL SYSTEM Homer ,T. Lambert and William B. vLutes, said Lutes assignor to Auto Specialties Manufacturing Company, St. Joseph, Mich, a corporation of Michigan Application October 1, 1940, Serial No. 359,766 6 Claims. (G1. 186-18) St. Joseph, Mich;

The present invention relates to tractors and particularly to mean for facilitating steering thereof by selective application of the brakes.

It is a general object of the invention to provide improved means to facilitate the making of sharp turns with a tractor by selective application of the brakes.

One more specific object of the invention is to provide means in connection with a wheeled tractor having a dirigible front wheel to facilitate making sharp turns by automatically rendering inoperative one of the rear wheel brakes when the front dirigible wheel has been turned beyond the angle required for normal turns, so that the driver may, by applying the brakes, actuate only the brake on the wheel on the inside of the curve.

Another object of the invention is to provide an improved device of the type described embodying auxiliary manual control means which may be operated at any time to control'the brake application regardless of the position of the dirigible wheel.'

Another object of the invention is to provide an assembly of 'a hydraulic master cylinder and selective valve mechanism for selectively controlling application of the brakes. I

Other objects and advantages of the invention will become apparent from the following specification, the accompanying drawings, and the appended'claims.

In the drawings:

Figure 1 is a side elevation of a conventional form'of tractor with parts being broken away to show some of the interior construction.

Figure 2 is a fragmentary end elevation taken on the line 22 of Figure 1. Figure 3 is a 'side view of the preferred master cylinder and control valve assembly with parts broken away and the valve housing cover removed.

Figure 4 is a top view of the master cylinder assembly of Figure 3 partly in section. I

Figure 5 is a fragmentary view, corresponding to Figure 3, showing the control valve in a diif erent position. i

Figure 6 is a fragmentary section taken on ,the line 6- -6 of Figure 4.

Figure 7 is a left end View of a master cylinder andcontrol valve assembly.

Figure 8 shows a fragmentary side elevation, partly in section, of a modified form of control valve adapted to be used with the master cylinder of the previous modification.

Figure 9 "is an end view of a modification shown fragmentarily in Figure 8.

Figure 10 is a side elevation of the valve element of the modification shown in Figure 8.

"Figure" 11 is an end view of the Valve element shown in Figure 1 0 Figure 12 shows an assembly View of a .further modification of the invention adapted for installation upon existing tractors which are already provided with master brake cylinders;'

Figure 13 is a section taken on the line |3-i3 of Figure 12 i Figure 14 is a section taken on the line [4-44 of Figure 13;

Figure 15 is a rear elevation of the manual control lever assembly, taken on the line i5i5 of Figure 12;

Figure 16 is a sectional view similar to the view shown in Fig. 4 of a further modified form of control valve which may be utilized in place of that illustrated in Fig. 4;

Figure 17 is a section taken on the line 17-47 of Fig. 16;

Figure 18 is a section taken on the line l8-i8 of Fig. 19 of the valve seat and sealing element utilized in the valve of Fig. '16;

Figure 19 is a top View of the valve seat element shown in Fig. 18;

Figure 20 is a sectional view of the valve element shown in Fig. 16; and,

Figure 21 is a top view of shown in Fig.20.

Referring to the drawings, there is shown in Figure 1 a view of a conventional tractor having a pair of driving wheels ill, one at each side of a transverse axle l l, mounted at the rear of the tractor. Only one of the driving wheels Ill appears in the View, the other being broken away toshow some of the interior construction. The tractor is provided with front Wheels i2 which are mounted in any conventional or suitable manner for steering and the wheels 12. are steered'by means of a steering wheel 13 which acts through a steering arm 14 and rod l5 in the usual manner. Each of the rear wheels of the tractor is provided with a hydraulic brake (not shown) which may be of any desired form and construction but is preferably of the type disclosed in the Homer T. Lambert Patents Nos. 2,963,444, 2,099,489, 2,161,359, and 2,161,360.

' The brakes of the rear wheels are energized by a-master cylinder assembly, shown best in Figures 3 to '7. This assembly comprises a unitary casting, indicated generally at is, which is provided with a central cylindrical bore l1, which is the brake master cylinder itself, a brake fluid reservoir H3 at one end of the cylinder IT and'a the valve element valve housing l9 at the opposite end of the cylinder H. The reservoir I8 is completed and closed by a cover plate which is held in place by any suitable means such as cap screws 2|, extending in suitable bosses 2| in casting IS. The reservoir is provided with a suitable filler opening closed by a plug 22. A brake operating pedal 23 is pivoted on a brake shaft 24 which extends into the reservoir l8 and carries an arm 25 which is connected by a pin 26 and a push rod 21 to a brake actuating piston 28 positioned within the cylinder H. A suitable spring 29 seats at one end against the casting l6 and at the other against a shoulder on the push rod 21 thereby acting in a direction to return the pedal to released position.

The piston 28 is provided with a rubber disc 30 on its forward face adapted to seal it against leakage between the piston and the cylinder wall. There is provided, however, a plurality of communicating passageways 3|, 32, and a central bore 33 by means of which fluid may under certain circumstances flow through the piston. Extending into the central bore 33 of the piston is valve rod 34 having its righthand extremity, which is located within the bore 33, of approximately square cross-section in order that fluid may flow past the rod 34 Within the bore 33. Welded to the rod 34 adjacent the piston 28 is a valve disc 35 having a seating edge 36 adapted when seated against the rubber disc 30 to close communication through the passages 3| and 32 and bore 33. A spring 31, positioned within the cylinder, normally acts upon the valve disc 35, forcing it against the piston thereby acting to maintain the valve closed and at the same time to urge the piston 28 toward brake release position. The lefthand extremity of the valve rod 34 is guided by means of a spider 38 having three legs 39, against the out-turned extremities of i which seats the spring 31. The snap ring 40 is seated within a suitable groove in the lefthand extremity of the valve rod 44 and acts to limit movement of the valve rod to the right under the influence of spring 31. tioned that when the foot pedal is released, spring 29 shifts the pedal and piston 28 far enough to the right so that a slight opening of valve 35, 36 occurs. As a result, when the brakes are in released position, fluid may flow from the reservoir l8 through passages 3| and 32 and bore 33 to the left-hand side of piston 38 thereby compensating for any leakage which might occur in the pressure lines to the brakes. The lefthand extremity of the cylinder I1 is connected by a counterbore 4| to passageway 42 to the interior of the valve housing !9.

The reservoir !8 is also connected to the interior of the valve housing H! by means of the intersecting passageways 43, 44, and 45. The bore 43 is positioned within an upstanding fin 46 which is provided with a pair of openings 41 for reception of bolts by means of which the assembly may be mounted on the frame of the tractor. The lefthand extremity of the bore 43 is closed by suitable plug 43.

A pair of fluid pressure brake lines 53 and 5| are connected by suitable fittings to the casting |6 in communication with intersecting bores which connect the pressure lines to the valve housing, the pressure line 53 being connected to the valve housing by intersecting passages 52 and 53, while the pressure line 5| is connected to the housing by passages 54 and 55. As best shown in Figure 3, the passages 45, 53, and 55 enter the The parts are so proporl:

valve housing at the back thereof through a back wall having a flat surface 56 adapted to receive the movable valve element 51. The valve ele ment 51 which seats against the face 56 is provided with an arcuate groove 58 in its back face of sufficient length, as best shown in Figure 5, to extend between and provide communication between the passageways 45 and 53 or between the passageways 45 and 55, depending upon the position of the valve element 51. The groove 53 is always in communication with passage 45 and the valve element 41 is normally held in the position shown in Figure 3, as will be hereinafter set forth, in which position the passage 45 is disconnected from both of the passages 53 and 55. A pair of stop pins 59 are provided for limiting movement of the valve element 51 in its two extreme positions.

The valve housing I9 is closed by means of a screw-threaded plug or cover plate 60 having a valve operating shaft 6| extending therethrough and provided with a flattened end portion 62 which is fitted within a suitable slot in the movable valve element 51. The bore in plug 60 through which the valve operating shaft 6| extends is provided with a counterbore 63 within which is seated a collar 64 welded to the valve shaft 6|. The collar 64 serves to prevent outward movement of the shaft 6| as the result of pressure existing within the valve housing. A suitable packing 65 surrounds the valve shaft 6| to prevent leakage. A spring 66 surrounding the valve shaft 6| seats at one end against the packing 65 and at the opposite end against the movable valve element 51, serving to hold the latter against the face 56.

The valve '51 which, as will be apparent, is of the four-way type, is operated by means of a lever 10, shown best in Figures 2 and 4, which is fixed to the valve operating shaft 6| and depends therefrom. The lower end of the lever 10 is provided with a stud 1| on which is pivoted a floating lever 12. The upper end of the floating lever is connected, as best shown in Figures 1 and 2, to a forwardly extending rod 13 which extends loosely through an opening in a stud 14 that projects laterally from the steering arm |'4. Suitable stop collars 15 and springs 16, surrounding the shaft 13 on opposite sides of the stud 14, serve to hold the rod 13 resiliently against sliding movement within the stud 14.

It will be apparent from the above that when the tractor is steered, movement of the steering arm M will tend to shift rod 13 and thereby the four-way valve 51. The parts are so arranged that the dirigible wheels I2 of the tractor must be turned through a predetermined angle before the valve 51 is shifted from the position shown in Figure 3 to the position shown in Figure 5, in which latter position one of the brakes is rendered inoperative. The angle through which the dirigible wheels |2 must be turned to complete shifting of valve 51 is a matter of choice, but it is preferred that this angle be in the order of 35 in order that normal steering movements of the wheels may be effected without affecting the braking system of the tractor. It is only when it is desired to make an abnormally sharp turn that it is necessary to apply the brakes to one of the tractors rear wheels and it is, therefore, quite important to prevent application of only a single rear wheel brake during normal maneuvering as accidents may otherwise occur.

It will be noted, as best shown in Figures 4 and 5, that when the valve 51 is shifted to its extreme counter-clockwise position, in which passages and .53 are connected and communication is closed between passage '53 and the interior of the valve housing. If the brakes are applied .when the valve is in this position, the fluid pressure from the master cylinder II passes through the passages M and 42 to the interior of the valve housing I9 and thence through passages 55 and 54 to the pressure line 5| which is connected to ,the' brake on the righthand driving wheel. It will be understood that valve 51 is shifted to this position when .the dirigible wheels I2 of the front of the tractor are turned to the right a predetermined amount, by reason of forward movement of the steering arm I4 and drag link I5. Thus, when the dirigible wheels I2 are turned to the right to the desired degree, and the driver desires to make a still sharper turn to the right, all he need do is apply the brake by means of the foot pedal 23, thereby stopping I the right driving wheel Ill and swinging the forward end of the tractor about the right driving Wheel by reasons of the propulsive effect of the le'fthand driving wheel. This enables the making of sharp turns at the ends of a row in plowing, cultivating, or the like with a minimum loss of time or expenditure of effort.

It should be noted that when the valve 57 is shifted to the left under these conditions, the brake line to the lefthand brake is vented through passages 52, 53, groove 58, passages 15, 44, and 43 to the reservoir. This insures that the lefthand brake will be fully released even though it may have been applied at the time valve 5? was shifted.

It will be understood that when the dirigible wheels I2 are turned to the left, rearward movement of the steering arm It which effects such steering movement will shift rod 73 to the rear thereby causing clockwise rotation of lever Hi and valve 51 when the desired amount of rightward turning has occurred. Communication between the brake cylinder I1 and passage 55 will be closed and the latter passage 55 will be vented tQ the reservoir through groove 58 and passage'45, etc. As a result, subsequent operation of the brake pedal will cause application of only the brake on the lefthand wheel thereby effecting a sharp left turn.

The lower end of lever 72 is connected by means of a rod TI to a hand lever IS mounted upon the tractor frame and associated with any suitable form of ratchet mechanism such as an arcuate bar I9 provided with notches (not shown) for engaging the lever I8 and holding it in any desired position of adjustment. It will be apparent, by reason of the fact that the lever 78 is connected .to the opposite end of the same floating lever I2 to which the steering arm I4 is connected, that it is possible by means of the handle I8 to shift valve 57 to any desired position at any time regardless of the position of the dirigible wheels I2, Accordingly, the driver can manipulate the brakes individually at will if desired.

In Figures 9 to 11, inclusive, is shown a modified form of the invention similar in all respects to that just described except that the four-way valve is of a different type and is positioned within a separate casting from the master cylinder. The master cylinder itself is identical to that previously described except that the casting of which it is formed terminates with a threaded bore 19.0 which communicates with the interior of the master cylinder 9| by means of a passage sageways .IIA and 92, The valve housing 93 is provided with a threaded nipple 94 which is threaded within the threaded bore'flll of the master cylinder casting. The valve housing is provided with a longitudinally extending bore 95 which is closed by means of 'a threaded plug 96, having a central opening 91 through which projects a valve operating rod 98.' Threaded on the rod 98 within the bore 95 is a cylindrical valve element indicated generally at I011, shown best in Figures 8, 9, and 10. A suitable packing ring IUI seals the valve housing against leakage around the valve stem 98. A spring I02 surrounds the stem 93 between the valve I00 and the packing ring IGI. This spring serves to hold the packing ring IIH in place and operates to :balance the valve element against the result of unequal areas at opposite ends thereof. The valve I00 is generally cylindrical in form and is provided with a longitudinally extending passageways I84 extending throughout its length in order to balance the pressures at opposite ends of the valve. Spaced at an angle of around the periphery of the valve Iill) are a pair of longitudinal slots Hi5 and N36 connected by a peripheral slot m1. Slot I in all positions of adjustment of the valve communi cates with a port H38 in the valve housing which, in turn, communicates through suitable fittings I99 with a pipe III) which is connected, in turn, to the reservoir II! by means of a fitting H2. The slot I85, when the valve is in its normal or central position, shown in Figure 8, does not communicate with anything. However, when the valve is shifted to the left, this "slot I06 communicates with a pipe H4 connected to a pressure line II5 leading to the brake on one of the rear wheels. When the valve I05 is in its righthand position, slot IE6 communicates with a passage I5 which in turn is connected to a pressure line II? which runs to the brake on the opposite rear wheel of the tractor. As a result, it will be noted that when the valve IN! is in the central position, pressure from the master cylinder 9i has free passage to both of the pas- IIB and, therefore, to both brakes of the tractor. However, when the valve I 00 is shifted to the left and the brakes applied, the fluid pressure from the master cylinder ill Will flow to passageway l I5 and pressure line I I! to one of the brakes, but no flow can take place to .the passage I14 or line H5 and the brake on the other wheel. .On the contrary, in this position of the valve, passage H4 and pressure line II-5 are connected through grooves I06, I51, and N35 to passageway I98 and line Ill) to the reservoir III, thus venting the brake connected to pressure line II5 and insuring release thereof. The opposite brake may be applied when the valve is shifted to its righthand position,

Valve IE0 is operated by means of a floating lever I28 pivoted intermediate its ends by means of a pin I.2I on the extremity of the valve operating valve 98. The upper end of lever I29 is connected by a rod I22 to the steeringarm of the tractor in the manner indicatedin Figure 1, while the lower end of floating lever I28 is connected by means of a rod I23 to any suitable form of hand lever provided with a suitable detent mechanism.

In this form of the invention, when the dirigible wheel I2 of the tractor are turned to the right a predetermined amount, forward movement of the steering arm [4 (Figure 1) will pull rod J22 .(Figure 8) to the right, shifting valve I518 to the ri t a d p m tt ep i ti 0f the brake connected to pressure line II5 which in this case should be the righthand brake. The lefthand brake is connected to pressure line II1.

In both of the previously described modifications of the invention, it will be understood that any type of steering mechanism for the front dirigible wheels may be provided and that any type of brake mechanism may be provided on each of the rear wheels. All that is required is that upon steering movement of the front dirigible wheels to the right, that only the righthand brake be in condition for application after the dirigible wheels have been turned beyond a predetermined angle and vice versa.

In Figures 12 to 15, inclusive, is shown a further modification of the invention in which the valve is mounted independently of the master cylinder. This form is adapted for application to tractors already provided with hydraulic braking systems. In this form, the invention provides a separate form of valve housing, indicated at I30, which is connected to the master brake cylinder (not shown) by means of a pressure conduit I3I and which is also connected by pressure conduits I32 and I33 to the individual rear wheel brake mechanisms, respectively. An additional fluid pressure conduit I34 also extends from the valve housing I30 to the usual fluid reservoir associated with the hydraulic brake master cylinder.

The valve housing is formed of a generally cup-shaped member I35 which, as indicated in Figure 14, has a hexagonal exterior surface adapted for application of a wrench thereto, and a closure cap I36 which is likewise hexagonally shaped and which is screw threaded into the cupshaped member I35, as best shown in Figure 13, to complete the housing. The conduits 3| to 34, inclusive, are connected directly to the cap member I36 by means of fluid passageways I31 to I40, inclusive, respectively. The latter passageways make right-angled turns, as best indicated in Figure 13, and enter the valve housing through the flat inner face I4I of the cap I36.

Mounted within a central bore in the cap I36 is a valve operating rod I43 having welded thereto a collar I44 which seats within a counterbore opening at the inner end of the central opening of the cap and serves to prevent outward movement of the collar I44 under the influence of internal pressure. A suitable packing ring I45 serves to prevent leakage around the valve rod. The inner extremity I46 of the rod I43 is flattened, as best shown in Figure 14, and extends into a slot or rectangular opening in a movable valve element I41. The valve element I41 is identical to the element 51 described in connection with the firstmodification and is provided with an arcuate groove I48 which is at all times in communication with passage I40. A pin I49, extending through the flattened portion I46 of the rod I43, serves to hold the movable valve element I41 on the rod and a spring I50, positioned between the bottom of the cup-shaped housing member I35 and the valve element I41 holds the latter against the flat face I4I of the cap I36 in order to prevent leakage.

As in the previous modifications of the invention, when the valve I41, as viewed in Figure 12, is shifted from its normal central position, shown in dotted lines in that figure, to its lefthand position, communication between the passage I31 and passage I38 is cut off and the passage I40 is connected to passage I38. As a result, upon actuation of the master cylinder under these conditions, fluid pressure from line I3I will pass through passage I39 and conduit I33 to only one of the rear wheel brakes, the brake on the other rear wheel being connected through line I32, passage I31, groove I48, passage I40, and line I34 to the fluid reservoir. When the valve I41 is shifted in the opposite direction or to the right, as viewed in Figure 12, these connections are reversed and the brake connected with line I32 is applied while the other brake is released.

Valve I41 is operated by means of a lever I52 fixed to the valve operating rod I43 and provided at its outer or lower end with a stud I53 upon which is pivoted a floating lever I54. The upper end of the floating lever is connected by means of a rod I55 to a member I56 which is fixed with respect to the steering column I51 of the tractor by any suitable means such as a nut I58. The member I51 is provided with an upstanding stud I59 through which the rod I55 slidably extends, the stud I59 being rotatable with respect to the member I56 to permit angular movement of the rod I 55 with respect to the member I56. Fixed to the rod I55, at opposite sides of the stud I59, are a pair of stop collars I60 and springs I6I are positioned between the stop collars and the stud for resiliently centering the rod I55 with respect to the member I56. The springs I6I are sufficiently stifi to effect a shifting of valve I41 when the steering column I51 is rotated, but they will yield to permit movement of member I56 and stud I59 after the valve I41 has come up against stop pins I52 for limiting movement of the valve element in either direction. It will be observed that when the steering column I51 is rotated to the right, as viewed in Figure 12, valve element I41 will be rotated to the left. Accordingly, the righthand brake should be connected to the pressure conduit I33 and the lefthand brake should be connected to pressure conduit I32.

The rear end of the floating lever I54 is connected by means of a rod I64 to a stud I65 rotatably positioned upon the hub I66 of a hand lever I61. The hub I66 is journalled upon a pin I 68 which is mounted upon a supporting plate I69 that may be mounted in fixed position in any suitable manner upon the tractor. The pin I68 is threaded at its outer end and provided with a nut I10 and a spring I1I is positioned between the nut I16 and the hub I66 of the hand lever in order to hold the hand lever resiliently against the plate I69. A pair of balls I 12 adapted to fit within complementary recesses in the hub I66 and plate I69 serve to resiliently hold the hand lever against displacement from its central position. It will be observed that by manual operation of the hand lever I61, valve I41 may be shiited at any time regardless of the position of the steering column and member I56.

In Figs. 16 to 21, inclusive, is shown an improved form of valve construction adapted to be utilized in place of the control valve 51 to 65, inclusive, in the form of construction shown in Figs. 3 to 6.

Referring to Fig. 16 there is shown fragmentarily a master cylinder indicated generally at I which master cylinder assembly may be similar in all respects to that illustrated in Figs. 3 and 4 except that there is omitted the passages 43 and 44 of the structure shown in Figs. 3 and 4 and there is utilized an improved form of control valve hereinafter described.

The control valve in the form of the invention shown in Figs. 16 to 21, inclusive, includes a casting indicated generally at I82 which is provided with a suitable cylindrical projection I 83 adapted tofit within a corresponding opening in theinaster cylinder member'ISfl and close that opening. A packing I84 is provided to prevent leakage at the opening and the casting I82 is secu'redto the master cylinder. element by means of four cap screws (not shown) which extend through the openings I85 in the casting I82. The casting I82 is provided with a central bore I86" i'n'which is fitted a valve operating shaft I81. A suitable operating lever I 38 is fixed to the shaft I81 by means of a nut I89, the arrangementbeing sim ilar to the mountingof lever III in Fi'gsf 1 to 6, inclusive. The cast-ing I82 is provided'with three passages I9Q, I91 and I92 extending parallel to the bore I86 entirely through the casting. The outer ends of the passages I90, I9! andlilz are counterbored and threaded for the reception of suitable pipe fittings as best shown in'connection with passages I90 and I92'in Fig. 16.

There is provided at the'inner side of the casting I82 a unitary rubber disc indicated generally at I95 whichserves thecombin'ed functions of a valve seat and also a seal for the bore L85, passages I99, I9I' and I92, as well as the opening within which the projection I83 of the casting I82 fits. This rubber disc, whichis best shown in Figs. 16, 18 and 19, is provided with a central opening through which the shaft IE'I' extends'a'nd an upstandingfin or cylindrical projection I95 which is forced against the shaft I81 by the in ternal pressure and serves to'seal the bore I88. A similar upstanding fin or projection I 91 is provided at the periphery of the disc N5 and serves to seal the opening in the master cylinder I89.

Intermediate the sealing'rims I35 "and IS! the disc is provided with a flatannular surface I93 which acts as a valve seat. The opposite side of the disc is provided with six pins or projections 29?, three of which fit within suitable openings formed in the casting I82 and the remaining three fit within counterbores for the passages I90, IQI and I82 as best shown in Fig. 16. The three projections which fit within the counterbores are provided with axial passageways 19,9, Isl. and I93 communicating with the passages I90, I9! and I92, respectively. These projections 29,0 serve to prevent rotation'oi" the valve seat disc with respect to the casting "I52 and the openings I99, ISI and I52 serve as extensions of the passages I 90, Ifil and I92 to the inner surface of the valve disc.

As best shown in Figs. 16, 20 and 21 there is provided a stamped sheet metal valve element indicated generally at 282 having an upstanding central portion provided with a square opening 2&3 adapted to fit upon a square extremity 204 on the valve operating shaft I87. A suitable pin 2st serves to prevent removal of the valve from the square extremity of the valve shaft. The peripheral portions of the valve 2% seat against the annular seating surface H8 on the rubber disc I95 and are provided with a pair of arcuate slots 20% and 201 adapted to cooperate with the openings I99 and I92 in the valve disc. The periphery of the valve 2E2 is also provided with a groove 293 in its under or valve seat contacting surface which groove overlies the opening lei in the valve disc in the manner best shown in clotted lines in Fig. 17. The arrangement is such that when the valve is in its central position, indicated in Figs. 16 and 17 of the drawings, passages I39 and 92 are in communication with the interior of the master cylinder E83 but no communication is provided between passageway IN and either of the passageways I30 or I92. When the valve 202 is rotated clockwise from the position shown in Fig. 17 fgroove 298 is moved into aposition in which it connects passages I 99 and IS'I while at'the'same time closing communication between the master cylinder I89 and 'the passage I93. At the'same' time because of the length of the slot 361, passage I92 remains in communication with the master cylinder. When the valve'is operated in the reverse direction passages l9! and I52 are connected'through groove 22% leaving only passage I9Il'in communication with the master cylinder I80. A helical spring 269 is provided for resilientlyurging the valve element 2? against its seat at all times." 7

As in the form of the invention described in greater detail in connection with Figs. 3 and 4, p ssa es '53 and I92 are onn te r sp tiv lyfto the brake mechanisms on the left and right hand driving wheels so that when the valve is rotated clockwise from the position shown in Fig. 1'7 and the brakes applied only the right hand driving wheel brake will be" applied and vice versa. The passageway ISI is connectedby any suitable pipinglnot shown) to the reservoir commonly associated with the master cylinder of the hydraulic brake mechanism and thus serves the same purpose as thepassageway 43- 44 in Figs. 3 and 4, namely the function of connecting the inoperative brake to the reservoir 'to insure release of the same.

It will be observed that the form of control valve just described operates to produce identically the same results'as the control valve'sdescribed in connection with the preceding modifications. It has been found, howeverjthat it operates more efliciently, is highly effective in preventing leakage and is exceedingly inexpensive to manufacture and assemble as compared with the variations previously "described.

It is apparent that'there are provided in accordance with the present invention several practical forms of brake applying and controlling mechanism adapted to facilitate steering of a tractorand particularly to supplement the normal steering operation accompanied by Totating front dirigible wheels. It will be apparent that various other modifications in the arrangement of the parts and details of construction -are available" within thespirit of the invention and within the scope of the'appended claims.

What is claimed is:

1. In a tractor having a pair of rearwardly positioned driving wheels, one on each side thereof, a front dirigible wheel, means for turning said dirigible wheel at an angle to the driving wheels to steer the tractor, a brake on each of said driving wheels, a common brake actuator for both of said brakes, a separate connection between said actuator and each brake, and means connected with said dirigible wheel turning means and actuated automatically when said dirigible wheel is turned more than a predetermined angle with respect to the rear wheels to render inoperative the connection between said actuator and the brake on the driving wheel located on the outside of the curved path traversed by the tractor when said dirigible wheel is so turned.

2. In a tractor having a pair of rearwardly positioned driving wheels, one on each side thereof, a front dirigible wheel, means for turning said dirigible wheel at an angle to the driving wheels to steer the tractor, a hydraulically actuated brake on each of said driving wheels, a brake master cylinder, a separate fluid connection between said master cylinder and each brake, and a valve connected with said dirigible wheel turning means and actuated automatically when said dirigible wheel is turned more than a predetermined angle with respect to the rear wheels to close the fluid connection between said master cylinder and the brake on the driving wheel located on the outside of the curved path traversed by the tractor when said dirigible wheel is so turned.

3. In a tractor having a pair of rearwardly positioned driving wheels, one on each side thereof, a front dirigible wheel, means for turning said dirigible wheel at an angle to the driving wheels to steer the tractor, a hydraulically actuated brake on each of said driving wheels, a brake master cylinder, a reservoir associated with said master cylinder, a separate fluid connection between said master cylinder and each brake, and means including a valve connected with said dirigible wheel turning means and actuated automatically when said dirigible wheel is turned more than a predetermined angle with respect to the rear wheels to close the fluid connection between said master cylinder and the brake on the driving wheel located on the outside of the curved path traversed by the tractor when said dirigible wheel is so turned, and to vent said last named fluid connection to said reservoir.

4. In a tractor having a pair of rearwardly positioned driving wheels, one on each side thereof, a front dirigible wheel, means for turning said dirigible wheel at an angle to the driving wheels to steer the tractor, a brake on each of said driving wheels, a common brake actuator for both of said brakes, a separate connection between said actuator and each brake, and means connected with said dirigible wheel turning means and actuated automatically when said dirigible wheel is turned more than a predeter mined angle with respect to the rear wheels to' render inoperative the connection between said actuator and the brake on the driving wheel located on the outside of the curved path traversed by the tractor when said dirigible wheel is so turned, and manual means operable at all times for controlling the operation of said last named means.

5. In a tractor having a pair of rearwardly positioned driving wheels, one on each side thereof, a front dirigible wheel, means for tuming said dirigible wheel at an angle to the driving wheels to steer the tractor, a hydraulically actuated brake on each of said driving wheels, a brake master cylinder, a separate fluid connection between said master cylinder and each brake, and a valve connected with said dirigible wheel turning means and actuated automatically when said dirigible wheel is turned more than a predetermined angle with respect to the rear wheels to close the fluid connection between said master cylinder and the brake on the driving wheel located on the outside of the curved path traversed by the tractor when said dirigible wheel is so turned, and manual means operable at all times for controlling the operation of said last named means.

6. In a tractor having a pair of rearwardly positioned driving wheels, one on each side thereof, a front dirigible wheel, means for tuming said dirigible wheel at an angle to the driving wheels to steer the tractor, a hydraulically actuated brake on each of said driving wheels, a brake master cylinder including a reservoir, a separate fluid connection between said master cylinder and each brake, a four-way valve in said fluid connections adapted in one position to close communication between the master cylinder and one of said brakes and vent the fluid connection to said brake to the reservoir, and adapted in another position to similarly close and vent the fluid connection to the other brake, said valve having a normal intermediate position in which both fluid connections pass without interruption to the master cylinder, an operating member for said valve, a floating lever pivoted on said operating lever, a connection between one end of said floating lever and said dirigible turning means effective to shift said four-way valve to close and vent one of said fluid connections when the dirigible wheel is turned beyond a predetermined angle with respect to the driving wheels in order to render inoperative the brake on the outside wheel, and manual means connected to the opposite end of the floating lever for actuating said valve independently of said dirigible wheel turning means.

HOMER T. LAMBERT. WILLIAM B. LUTES. 

